Why is an unconventional hydrocarbon reservoir unconventional? An investigation into petrophysical and fluid composition controls.

为什么非常规油气藏是非常规的？

• 批准号: RGPIN-2018-05695
• 负责人: Harris, Nicholas
• 金额: $ 3.64万
• 依托单位: University of Alberta
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=750898
• 关键词: Why; unconventional; hydrocarbon; reservoir; investigation

Unconventional petroleum reservoirs represent the largest fraction of remaining hydrocarbon reservoirs in the world. The most striking feature of these reservoirs, in addition to low permeability, is the unusual, unpredictable nature of fluid distributions: the lack of an obvious top seal and less dense (more buoyant) fluids underlying more dense fluids. Thus, gas or oil can accumulate in low permeability formations that underlie high permeability formations, and gas pools may underlie water or oil columns. Petrophysical properties and capillary forces clearly underpin the unusual distribution of fluids in unconventional petroleum accumulations, which are not found in high permeability formations. In multiphase systems, buoyant forces are balanced against surface tension at the fluid interfaces and the wettability of fluids on solid materials. Thus, shales seal hydrocarbons below a sandstone-shale contact, even though the overlying shale maybe water-saturated. If this applies to unconventional reservoirs, some combination of rock fabric (composition plus texture) interacts with fluid properties (buoyancy, composition, surface tension) to produce unusual segregations of fluids. But how fluid and petrophysical properties control fluid distributions is not understood.Four reservoir units provide natural laboratories for testing models that describe unconventional reservoirs: (1) the hydrocarbon-rich Montney Formation in western Canada that contains conventional hydrocarbon accumulations where it is shallow (distinct top seal, gas over oil over water) but unconventional accumulations where it is deep (no distinct top seal, variable and unsystematic fluid distributions); (2) the Upper Cretaceous large tight-gas-sand accumulations in the U.S. Rocky Mountains where lower permeability reservoirs underlie high permeability caprocks; (3) Lower Cretaceous tight oil/gas sandstones in Alberta with complex pore systems that require hydraulic stimulation to produce; and (4) Duvernay Formation, a shale liquids reservoir where rocks are variably oil-wet, water-wet and have mixed wettability in different parts of the reservoir.I will combine field data and quantitative modeling to develop models for fluid distributions in unconventional reservoirs and to identify tipping points that distinguish conventional from unconventional accumulations. Computationally powerful software can simulate migration of hydrocarbon fluids under the influence of both capillary and buoyancy forces. Such software has not previously been applied to unconventional petroleum systems and may require additional development. This analysis will, in the end, yield new, more precise models for hydrocarbon migration, trapping and distribution in unconventional petroleum systems, tested on important petroleum systems in Canada and the United States and globally applicable.

非常规油气藏是世界上剩余油气藏中最大的一部分。除了低渗透率外，这些储层最显著的特征是流体分布的不寻常和不可预测的性质：缺乏明显的顶部密封，密度较小（浮力较大）的流体位于密度较大的流体之下。因此，天然气或石油可以聚集在高渗透地层下面的低渗透地层中，气藏可能位于水柱或油柱下面。岩石物理性质和毛细力明显支持非常规油气聚集中流体的不寻常分布，这在高渗透率地层中是不存在的。在多相系统中，浮力与流体界面的表面张力和流体对固体材料的润湿性相平衡。因此，页岩将碳氢化合物密封在砂岩-页岩接触层下方，即使上覆的页岩可能含水饱和。如果这适用于非常规储层，岩石结构（成分加纹理）的某种组合与流体性质（浮力、成分、表面张力）相互作用，会产生不寻常的流体分离。但流体和岩石物理性质如何控制流体分布尚不清楚。四个储层单元为描述非常规储层的测试模型提供了天然实验室：(1)加拿大西部富油气的蒙特尼组，其浅层包含常规油气聚集（明显的顶封，气盖油盖水），而深层则包含非常规油气聚集（没有明显的顶封，流体分布多变且不系统）；(2)美国落基山脉上白垩统大型致密气砂聚集，低渗透储层位于高渗透盖层之下；(3) Alberta地区下白垩统致密油气砂岩，孔隙系统复杂，需要水力增产；(4) Duvernay组为页岩液体储层，其岩石具有不同的油湿性和水湿性，并且在储层的不同部分具有混合润湿性。我将结合现场数据和定量建模来开发非常规油藏流体分布模型，并确定区分常规油气藏和非常规油气藏的临界点。计算功能强大的软件可以模拟油气流体在毛细力和浮力共同作用下的运移。这种软件以前没有应用于非常规石油系统，可能需要额外的开发。这种分析最终将产生新的、更精确的非常规石油系统中油气运移、圈闭和分布模型，并在加拿大和美国的重要石油系统中进行测试，并在全球范围内适用。